1. Technical Field
The present invention relates to a liquid ejection head and a liquid ejection apparatus. In particular, the invention is useful when being applied to a case where a drive waveform of the liquid ejection head is appropriately selected in order to control discharge characteristics in accordance with a temperature of liquid to be ejected.
2. Related Art
As an ink jet recording head as a representative example of a liquid ejection head which ejects liquid droplets, there is the following ink jet recording head, for example. That is, there is an ink jet recording head which includes a flow path formation substrate on which pressure generation chambers are formed, and piezoelectric actuators which are provided on one surface of the flow path formation substrate so as to correspond to the pressure generation chambers. Further, the ink jet recording head ejects ink droplets through nozzle openings, which are formed on a nozzle plate so as to penetrate through the nozzle plate in a thickness direction thereof, by applying a pressure into the pressure generation chambers with displacement of the piezoelectric actuators.
Discharge characteristics of ink by the ink jet recording head of this type depend on viscosity of the ink and the viscosity of the ink depends on a temperature thereof. Then, the following control is performed. That is, a drive waveform by which the piezoelectric actuators are driven is appropriately selected and changed in accordance with a temperature measured by a thermistor.
However, the existing thermistor is arranged on a circuit substrate as one of electric parts. Accordingly, in this case, the thermistor measures an ambient temperature, resulting in a large temperature difference between an actual temperature of ink to be discharged through the nozzle openings and the measured temperature.
In order to improve the discharge characteristics of ink, it is required to measure the temperature of ink to be discharged more accurately. Configurations disclosed in JP-A-2004-345109 and JP-A-2006-205735 have been proposed as devices for measuring a temperature of ink to be discharged through nozzle openings more accurately.
In JP-A-2004-345109, the recording head is formed by bonding a heat generation substrate and a flow path substrate and a temperature sensor is embedded in the heat generation substrate.
In JP-A-2006-205735, a thermistor as a temperature detection sensor is arranged on an upper surface of an insulating film while the thermistor and a lower electrode formed on a flow path formation substrate are ensured to be insulated from each other with the insulating film.
As described above, in JP-A-2004-345109, the temperature sensor is provided so as to be embedded in the heat generation substrate in a state where the temperature sensor makes contact with ink. Therefore, it may be considered that there is still a problem in that insulation of electrodes and the like thereof is not ensured. Further, in JP-A-2006-205735, the temperature detection sensor is arranged on the upper surface of the insulating film while the temperature detection sensor and the lower electrode formed on the flow path formation substrate are ensured to be insulated from each other with the insulating film. Therefore, there are problems in that a configuration of this portion is complicated and further temperature measuring accuracy is lowered because the temperature of ink is measured through the lower electrode film and the insulating film.
It is to be noted that the above problems arise not only in the ink jet recording head which discharges ink but also in a liquid ejection head which ejects liquid other than ink.